1. Field of the Invention
The present invention relates to a rotation hoop knife splitting machine, particularly for splitting skin which is free from hair. The machine includes a feeding device arranged in front of the cutting edge of the knife, wherein a transport gap defined by a base and a driven transport roll and a feeding gap defined by a base and a driven feeding roll are arranged closely one behind the other.
2. Description of the Related Art
A rotation hoop knife splitting machine of the above-described type is disclosed in DE 197 14 592 A1. The transport roll as well as the feeding roll are cylindrically shaped and interact with a plane base which, in the described embodiment, is stationary. The separation of the transport function from the feeding function makes it possible to carry out very accurate splitting, even in the case of material which is difficult to split, such as skin which is free from hair.
It is the primary object of the present invention to facilitate feeding of the material to be split and to further improve the splitting accuracy.
In accordance with the present invention, the transport roll has a diameter which increases toward the ends of the transport roll, wherein the transport roll is composed of at least two parts which are connected to each other in an articulated manner so as to rotate together, and wherein the two parts of the transport roll are mounted in such a way that the surface line of the transport roll at the transport gap is a straight line extending parallel to the base.
The configuration according to the present invention results in transport speeds of the transport roll which increase from the center toward the outside. This provides the following advantage: conventionally, a skin, for example, cowhide leather, is cut at the belly line and is placed in the correct plane for travel through the rotation hoop knife splitting machine. The belly area has a larger surface and a looser structure than the back area. If such a skin is moved by means of a cylindrical transport roll, the belly area is held up during the transport of the skin, while the middle portion along the back line essentially travels ahead of the belly area. This can be compensated by strongly decelerating the skin in the middle portion thereof either manually or by means of a braking device. However, if the transport roll according to the present invention is used, the conicicity of the roll results in higher circumferential speeds at the outer areas. Since no slippage or only little slippage occur in the transport gap, the skin is inevitably transported in the end areas at a higher speed than the rest of the skin and, consequently, the skin is stretched transversely of the transport direction. As a result, the belly area is essentially not held up and very accurate splitting is possible.
In accordance with an advantageous feature, the transport roll is composed of two cone-shaped parts. This means that the transport roll is of simple construction with only one coupling in the middle of the transport roll.
In accordance with another advantageous feature, two outer bearings and a middle support bearing are provided for the transport roll. The support bearing makes it possible in a simple manner to maintain in the support gap the desired straight surface line of the transport roll.
Preferably, the change of the diameter of the transport roll from the center to the outer ends is at least 5%. The best results are obtained if the increase is 15% or more. In accordance with an example, the transport roll has a diameter of 76 mm in the middle and a diameter of 90 mm at the ends.
In accordance with a recommended feature, the parts of the transport roll are connected to each other through a curved teeth connection, as it is known to be used in a curved teeth coupling. However, other conventional articulated couplings are also conceivable.
It is advantageous if, in the area of the transport roll having the greatest diameter, the circumferential speed of the feeding roll is at least equal to the circumferential speed of the transport roll. This ensures that the material which is transported at a greater speed in the area of the belly is moved toward the cutting edge of the knife in such a way that the skin is not held back and a more uniform cut can be achieved.
It is also advantageous if the transport roll is constructed as a rotary stretcher. This results in an increased stretching of the material to be split transversely of the conveying direction.
In accordance with an advantageous feature, the base of the transport gap includes an endless belt which is guided around a bottom roll which can be biased by means of a contact pressure device in the direction toward the transport roll. Such a feeding device with a moveable base is always recommended over a stationary base if the material to be split for histological reasons and reasons of body shape poses similar problems during cutting as a limed skin material, but that does not have the sliding properties of the latter.
In particular, the bottom roll may be supported by levers, wherein the contact pressure device in the form of a piston-cylinder unit acts on the levers. This results in a simple construction.